DARRINGTON, Washington (Reuters) - Rescuers searching for 90 people still missing five days after a massive Washington state mudslide said they expect the death toll to climb sharply soon, even as they clung to hope on Thursday of finding a miracle survivor.

At least 25 people are known to have died when a rain-soaked hillside collapsed without warning on Saturday, unleashing a wall of mud that engulfed dozens of homes in a river valley near the rural town of Oso, 55 miles northeast of Seattle.

Only the first 16 victims recovered and examined by coroners have so far been officially counted as dead, although local fire district chief Travis Hots said that figure would soon spike upwards. Nine more bodies that have since been found have yet to be added to the official toll.

"In the next 24 to 48 hours, as the medical examiner's office catches up with the difficult work that they have to do, you're going to see these numbers increase substantially," he said.

Snohomish County officials said on Wednesday that about 90 people remained missing or unaccounted for, down from an earlier estimate that was nearly twice that number, and Hots said on Thursday the revised figure was holding. An estimated 180 people lived in the path of the landslide.

Authorities have acknowledged there is little chance of finding any more survivors in the square-mile heap of mud-caked debris and muck left by the landslide, and that the remains of some victims may never be recovered.

Everyone who was discovered alive in the mud pile was rescued by helicopter within the first few hours after the landslide, and rescuers have not found further signs of life, officials said.

Still, Hots said a round-the-clock search effort by more than 200 people, who were painstakingly combing through a disaster site that included "clay balls the size of ambulances," would press on indefinitely.

"We're not changing the pace of this. And we're going to exhaust all options to try to find somebody alive," he said. "If we find just one more person that's alive, to me, that's worth it."

He said rain expected to last through the day could hamper search efforts, "so it's going to be a very difficult day."

GRIEF AND RECRIMINATIONS

As the days wore on, emotions were running raw among loved ones of the dead and missing, and the crews of people searching for them.

Jessica Neal, 30, said she found comfort from Wednesday's recovery of the body of her father-in-law, Steve Neal, a hot water heater installer who was working at a house hit by the slide, and in learning that he apparently did not suffer long.

"The coroner had details that it was fast," she said, as she fought back tears.

In this Wednesday, April 16, 2014, photo, a worker with a search dog stands next to a wrecked truck …

Shayne Barco, 37, a search team member from Bellingham who arrived at the site on Monday with his trained search dog, a German shepherd named Stratus, said he has labored to keep his emotions pushed to the side while he works.

"It really doesn't hit you until the day's over," he said. "We're out there digging through people's lives, doing the best we can to bring closure to some of the families. It's just take it day by day, chunk by chunk of debris."

As the potential enormity of the tragedy sinks in, many area residents have voiced a sense of anger that local officials refused to allow volunteers to join the frantic search for victims immediately after the slide, when chances for finding survivors were greatest.

While some used their intimate knowledge of the area to sneak into the disaster zone, others returned home feeling frustrated and helpless.

"I went the first day but we got roadblocked," said Calvin Burlingame, 62, a retired lumber mill worker who lives a few miles east of the slide and whose nephew is among the missing. "I'm upset that they did that because ... the community could have done a lot on our own."

Burlingame said he understood the risks involved but said it was worth it: "If we give up something to get something for somebody else, then that's OK."

State police spokesman Bob Calkins said conditions were simply too dangerous to allow non-professional volunteers into the disaster zone immediately after the slide.

"We wish they could have helped, too," Calkins said. "It would not have been safe, and we'd have had more victims."

'NEED A MIRACLE'

Community members from Oso and nearby towns assembled late Wednesday to offer prayers for the missing.

"We know, and most of us, I think, are accepting that many of our people are not going to make it," Megan Fanning, 41, said at the gathering in Darrington, not far from Oso. "But please, we need a miracle. Just one. One little miracle would be wonderful."

The community college student noted that the 14-year-old son of a close friend remained among the missing.

The casualty count has pushed the Oso mudslide into the history books as one of the deadliest, said Josef Dufek, a professor at Georgia Institute of Technology who studies natural cataclysms.

He pointed to the 1980 eruption of Mount St. Helens in Washington, which killed 57 people, and a 1969 landslide in Nelson County, Virginia, that killed 150.

Many valley residents have channeled their collective trauma into acts of comfort for the bereaved and support for searchers.

"This is a very strong community. ... We all stick together," said 25-year-old Jamie Olsen, as her husband and about 40 people in Darrington sorted water, food, diapers and other supplies for families forced out of their homes.

President Barack Obama has signed an emergency declaration ordering U.S. government assistance to supplement state and local relief efforts. A local disaster relief account had nearly $50,000 in it by Thursday.

Eight more people survived the slide but were injured, including a 22-week-old baby rescued with his mother. The baby was listed in critical condition but was improving. The mother and three other survivors remained hospitalized.